Claire Derry told the Sydney Morning Herald that her son, Sam Derry-Woodhead, 18, told her he drank contact lens fluid to keep going during his ordeal.
''He tried drinking his own urine and ... he wasn't able to cope much with that,'' she said. ''So he drank tiny sips of the contact lens fluid."
Derry-Woodhead was in Australia during his "gap year" between high school and university. He got lost Tuesday in a remote area in Queensland.
His mother said she boarded a plane at Heathrow International Airport fearing her son was dead. She had learned that most people do not survive in the harsh conditions of the Australian Outback.
While the plane was in the air, a member of the crew gave her the news that her son had been found.
''I screamed and hugged him and hugged the rest of the crew and they brought me champagne to celebrate,'' she said.
Two of the people looking for Derry-Woodhead were hospitalized with suspected heatstroke. His mother said he told her in a telephone conversation after she landed in Australia that rescuers told him they expected to find him with his "eyes pecked out."